Repetitive transcranial magnetic stimulation treatment of major depressive disorder and comorbid chronic pain: response rates and neurophysiologic biomarkers.

BACKGROUND: Major depressive disorder (MDD) and chronic pain are highly comorbid, and pain symptoms are associated with a poorer response to antidepressant medication treatment. It is unclear whether comorbid pain also is associated with a poorer response to treatment with repetitive transcranial magnetic stimulation (rTMS). METHODS: 162 MDD subjects received 30 sessions of 10 Hz rTMS treatment administered to the left dorsolateral prefrontal cortex (DLPFC) with depression and pain symptoms measured before and after treatment. For a subset of 96 patients, a resting-state electroencephalogram (EEG) was recorded at baseline. Clinical outcome was compared between subjects with and without comorbid pain, and the relationships among outcome, pain severity, individual peak alpha frequency (PAF), and PAF phase-coherence in the EEG were examined. RESULTS: 64.8% of all subjects reported pain, and both depressive and pain symptoms were significantly reduced after rTMS treatment, irrespective of age or gender. Patients with severe pain were 27% less likely to respond to MDD treatment than pain-free individuals. PAF was positively associated with pain severity. PAF phase-coherence in the somatosensory and default mode networks was significantly lower for MDD subjects with pain who failed to respond to MDD treatment. CONCLUSIONS: Pain symptoms improved after rTMS to left DLPFC in MDD irrespective of age or gender, although the presence of chronic pain symptoms reduced the likelihood of treatment response. Individual PAF and baseline phase-coherence in the sensorimotor and midline regions may represent predictors of rTMS treatment outcome in comorbid pain and MDD.

Preventing the Transmission of Murine Norovirus to Mice (Mus musculus) by Using Dry-heat Sterilization.

A critical component of an animal care biosecurity plan includes the sterilization of materials that come into direct contact with the animals. Dry-heat sterilization is gaining popularity in animal research facilities due to lower cost, less space utilization, no water usage, and the ability to sterilize water-sensitive materials. Currently, dry-heat sterilization ovens are validated against Bacillus atropheus spore strips with the assumption that a lack of sporulation is equivalent to successful sterilization. However, no published studies describe sterilization of rodent cages that contain relevant rodent pathogens by using this method. To determine if a dry-heat sterilizer can sterilize rodent cages and bedding against relevant rodent pathogens, we created murine norovirus (MNV)-contaminated cages by using mice with known MNV infection and shedding. The contaminated cages were either sterilized with the dry-heat sterilizer or not sterilized. Naïve, 4-wk-old, CD-1 mice were placed in the dry-heat-sterilized cages, contaminated unsterilized cages, or standard autoclaved cages for 2 wk. The mice were subsequently placed into clean, autoclaved cages for the remainder of the study. Fresh fecal pellets were collected at weeks 0, 12, and 16 and submitted for MNV PCR. Whole blood was collected for MNV serology at weeks 0, 8, 12, and 16. At week 16, all mice that had been in the unsterilized contaminated cages were positive for MNV by both fecal PCR and serology, whereas the mice in the dry-heat-sterilized and autoclaved cages were negative for MNV by both methods at all time points. Our study supports the use of dry heat sterilization as a viable sterilization method for rodent cages and bedding.

Sequential Prefrontal and Temporoparietal Repetitive Transcranial Magnetic Stimulation (rTMS) for Treatment of Tinnitus With and Without Comorbid Depression: A Case Series and Systematic Review.

Background: Tinnitus distress is related to both the loudness and intrusiveness of the tinnitus percept. Treatment approaches targeting both attentional/limbic and auditory systems may better alleviate tinnitus distress than approaches targeting the auditory system alone. Materials and Methods: Ten subjects with chronic tinnitus received sequential rTMS treatment involving: 1) excitatory stimulation administered to the left dorsolateral prefrontal cortex (DLPFC) or inhibitory stimulation administered to the right DLPFC, followed by 2) inhibitory stimulation administered to primary auditory cortex (Heschel's gyrus or HG). A systematic literature review was performed to evaluate the existing literature on sequential repetitive Transcranial Magnetic Stimulation (rTMS) treatment approaches for tinnitus. Results of the case series are interpreted in the context of tinnitus neurobiology and the extant literature. Results: Subjects experienced a significant decrease (average 21.7%) in symptoms on the Tinnitus Functional Index (TFI). Those with tinnitus alone experienced a greater mean symptom reduction than those with comorbid MDD (27.7 vs. 17.0%, respectively). Adverse effects were transient and minor. Literature review confirmed that sequential approaches had some advantages compared to single site rTMS; in general, the addition of 1 Hz treatment at DLPFC was superior to single site rTMS in the short term (1-12 weeks), while the addition of 20 Hz treatment at DLPFC appeared superior in the long term (90-180 days). Conclusions: Sequential rTMS approaches for the treatment of tinnitus-particularly those administering low-frequency treatment at left DLPFC-merit further investigation.

Treatment of Spider Phobia Using Repeated Exposures and Adjunctive Repetitive Transcranial Magnetic Stimulation: A Proof-of-Concept Study.

Background: Specific phobias represent the largest category of anxiety disorders. Previous work demonstrated that stimulating the ventromedial prefrontal cortex (vmPFC) with repetitive Transcranial Magnetic Stimulation (rTMS) may improve response to exposure therapy for acrophobia. Objective: To examine feasibility of accelerating extinction learning in subjects with spider phobia using intermittent Theta Burst Stimulation (iTBS) rTMS of vmPFC. Methods: In total, 17 subjects with spider phobia determined by spider phobia questionnaires [Spider Phobia Questionnaire (SPQ) and Fear of Spiders questionnaire (FSQ)] underwent ratings of fear of spiders as well as behavioral and skin conductance data during a behavioral avoidance test (BAT). Subjects then received a sequential protocol of in vivo spider exposure followed by iTBS for three sessions administered to either active or control treatment sites (vmPFC [n = 8] or vertex [n = 9], respectively), followed 1 week later by repetition of questionnaires and BAT. Results: All subjects improved significantly regardless of group across both questionnaires (FSQ η2 = 0.43, p = 0.004; SPQ η2 = 0.39, p = 0.008) and skin conductance levels during BAT (Wald χ2 = 30.9, p < 0.001). Subjects in the vmPFC group tolerated lower treatment intensity than in the control group, and there was a significant correlation between treatment intensity, BAT subjective distress improvement, and physiologic measures (all ρ > 0.5). Conclusion: This proof-of-concept study provides preliminary evidence that a sequential exposure and iTBS over vmPFC is feasible and may have rTMS intensity-dependent effects on treatment outcomes, providing evidence for future areas of study in the use of rTMS for phobias.

Absence of early mood improvement as a robust predictor of rTMS nonresponse in major depressive disorder.

BACKGROUND: Symptoms of major depressive disorder (MDD) are reported to change early in treatment with repetitive transcranial magnetic stimulation (rTMS). We evaluated early changes in sleep, anxiety, and mood as predictors of nonresponse to rTMS treatment. METHODS: Three hundred twenty-nine subjects with nonpsychotic MDD completed a 6-week course of rTMS treatment. Subjects were stratified by the severity of their baseline depression, and had their overall depressive symptoms recorded every week of treatment. We evaluated lack of improvement in sleep, anxiety, and mood symptoms after 1 and 2 weeks as potential predictors of eventual nonresponse, defined as <50% improvement in compositive depressive symptoms after 6 weeks. This was measured as negative predictive value (NPV; the likelihood that lack of early symptom improvement accurately predicted eventual treatment nonresponse). RESULTS: Subjects with severe or very severe baseline depression achieving <20% improvement in mood at 1 week were correctly predicted as nonresponders with NPVs largely >90%. At 2 weeks, subjects with very severe baseline depression who failed to demonstrate any improvement in mood were all nonresponders. Lack of improvement in sleep at 2 weeks was also a significant predictor. CONCLUSIONS: Identifying a lack of early mood improvement is a practical and robust method to predict rTMS nonresponse. This suggests a treatment protocol change may be indicated in patients with more severe baseline depression showing minimal early mood improvement.

Endonasal Endoscopic Fenestration of Rathke's Cleft Cysts: Whether to Leave the Fenestration Open or Closed?

Introduction Rathke's cleft cysts (RCC) are generally treated with transsphenoidal fenestration and cyst drainage. If no cerebrospinal fluid (CSF) leak is created, the fenestration can be left open. If CSF is encountered, a watertight closure must be created to prevent postoperative CSF leak, though sellar closure has theoretically been linked with higher recurrence rate. In this study, we investigate the relationship between sellar closure, rate of postoperative CSF leak, and RCC recurrence. Methods Retrospective review of a prospective database of all endoscopic endonasal RCC fenestrations and cases were divided based on closure. The "open" group included patients who underwent fenestration of the RCC, whereas the "closed" group included patients whose RCC was treated with fat and a rigid buttress ± a nasoseptal flap. The rate of intra- and postoperative CSF leak and radiographic recurrence was determined. Results The closed group had a higher rate of suprasellar extension (odds ratio [OR]: 8.0, p = 0.032) and intraoperative CSF leak ( p ≤ 0.001). There were 54.8% intraoperative CSF leaks and no postoperative CSF leaks. Radiologic recurrence rate for the closed group (35.0%) was three times higher than the open group (9.1%; risk ratio [RR] = 3.85, p = 0.203), but not powered to show significance. None of the radiologic recurrences required reoperation. Conclusion Maintaining a patent fenestration between an RCC and the sphenoid sinus is important in reducing the rate of radiographic recurrence. Closure of the fenestration may be required to prevent CSF leak. While closure increases the rate of radiographic recurrence, reoperation for recurrent RCC is still an uncommon event.

Subthreshold stimulation intensity is associated with greater clinical efficacy of intermittent theta-burst stimulation priming for Major Depressive Disorder.

BACKGROUND: Intermittent theta-burst stimulation priming (iTBS-P) can improve clinical outcome of patients with Major Depressive Disorder (MDD) who do not show early benefit from 10 Hz stimulation of left dorsolateral prefrontal cortex (DLPFC), also known as high-frequency left-sided (HFL) stimulation. The intensity and pulse number for iTBS-P needed to induce clinical benefit have not been systematically examined. OBJECTIVE: To study the effect of intensity and pulse number on the clinical efficacy of iTBS-P. METHODS: We conducted a retrospective review of 71 participants who received at least five sessions of HFL with limited clinical benefit and received iTBS-P augmentation for between 5 and 25 sessions. Intensity of iTBS-P priming stimuli ranged from 75 to 120% of motor threshold (MT) and pulse number ranged from 600 to 1800. Associations among intensity, pulse number, and clinical outcome were analyzed using a mixed methods linear model with change in IDS-SR as the primary outcome variable, priming stimulation intensity (subthreshold or suprathreshold), pulse number (<1200 or >1200 pulses), and gender as fixed factors, and number of iTBS-P treatments and age as continuous covariates. RESULTS: Subjects who received subthreshold intensity iTBS-P experienced greater reduction in depressive symptoms than those who received suprathreshold iTBS-P (p = 0.011) with no effect of pulse number after controlling for stimulus intensity. CONCLUSIONS: Subthreshold intensity iTBS-P was associated with greater clinical improvement than suprathreshold stimulation. This finding is consistent with iTBS-P acting through homeostatic plasticity mechanisms.

Strategies for augmentation of high-frequency left-sided repetitive transcranial magnetic stimulation treatment of major depressive disorder.

BACKGROUND: Repetitive Transcranial Magnetic Stimulation (rTMS) is an effective intervention for treatment-resistant Major Depressive Disorder (MDD). Early improvement during high-frequency left-sided (HFL) stimulation of the dorsolateral prefrontal cortex (DLPFC) is an important predictor of longer-term outcome, but most patients benefit later in their treatment course. We examined patients without early improvement with HFL to determine whether augmentation with additional stimulation approaches improved treatment outcome. METHODS: 139 participants received HFL in a measurement-based care paradigm. Participants who achieved < 20% improvement by treatment 10 could continue with HFL (N = 17) or receive one of two augmentation strategies: bilateral stimulation (BL; HFL followed by low-frequency stimulation of right DLPFC) (N = 69) or intermittent theta-burst priming of left DLPFC (iTBS-P) (N = 17) for their remaining treatment sessions. The primary outcome was the percent reduction in depressive symptoms at treatment 30. RESULTS: Participants who achieved < 20% improvement by treatment 10 and continued with HFL showed limited benefit. iTBS-P participants had significantly greater improvement, while those receiving BL trended toward improved outcomes. Ten sessions of either augmentation strategy appeared necessary to determine the likelihood of benefit. CONCLUSIONS: Augmentation of early non-response to HFL appears to improve rTMS outcomes, with a novel iTBS-P strategy surpassing both continued HFL or BL treatment in participants with < 20% improvement after 10 treatments. These findings suggest that measurement-based care with addition of augmented stimulation for those not showing early improvement may yield superior rTMS treatment outcomes.

Intraperitoneal Alfaxalone and Alfaxalone-Dexmedetomidine Anesthesia in Sprague-Dawley Rats (Rattus norvegicus).

Due to their unpredictability and variable effects, injectable anesthetic regimens in laboratory rodent species warrant refinement. In our study we sought to evaluate alfaxalone, which has gained recent popularity in veterinary medicine, alone and in combination with dexmedetomidine to evaluate their anesthetic ability in Sprague-Dawley rats when administered intraperitoneally. Three doses of alfaxalone only and 4 dose combinations of alfaxalone-dexmedetomidine were tested in males and female rats. The time to induction, anesthetic duration, pulse rate, respiratory rate, temperature, and time to recovery were recorded by a blind observer. The level of anesthesia induced by the various anesthetic protocols was assessed by using pedal withdrawal reflex to a noxious stimulus and scored according to the response. Dependent on the treatment group, atipamezole or saline was administered intraperitoneally once animals reached 60 min of anesthesia. Regardless of the dose, alfaxalone alone achieved only a sedative level of anesthesia, whereas all alfaxalone-dexmedetomidine combinations led to a surgical level of anesthesia in all animals. Anesthesia regimens using alfaxalone alone and in combination with dexmedetomidine demonstrated sex-associated differences, with female rats maintaining longer durations of sedation or anesthesia than their male counterparts. Both male and female rats displayed decreases in physiologic parameters consistent with the effects of dexmedetomidine. Given the results described herein, we recommend 20 mg/kg alfaxalone for sedation and 30 mg/kg alfaxalone combined with 0.05 mg/kg dexmedetomidine for surgical anesthesia in female rats. Appropriate doses of alfaxalone only and alfaxalone-dexmedetomidine for male rats were not determined in this study and need further evaluation.

Prefrontal Cortical Reactivity and Connectivity Markers Distinguish Youth Depression from Healthy Youth.

Up to 50% of youth with depression do not respond to conventional first-line treatments. However, little research has been conducted on the pathophysiology of youth depression, hindering the identification of more effective treatments. Our goal was to identify neurophysiological markers that differentiate youth with depression from healthy youth and could serve as targets of novel treatments. We hypothesized that youth with depression would exhibit network-specific cortical reactivity and connectivity abnormalities compared with healthy youth. Transcranial magnetic stimulation combined with electroencephalography and magnetic resonance imaging was employed in combination with clinical and behavioral assessments to study cortical reactivity and connectivity in bilateral dorsolateral prefrontal cortex (DLPFC), motor cortex, and inferior parietal lobule, sites linked to the frontoparietal network, sensorimotor network, and default mode network, respectively. In youth depression, greater cortical reactivity was observed specific to the left and right DLPFC stimulation only, which correlated with anhedonia scores. Additionally, the connectivity of the right DLPFC was significantly higher in youth depression. Source reconstruction attributed the observed connectivity dysregulation to regions belonging to the default mode network. The neurophysiological signatures identified in this study have high potential to inform the development of more effective and targeted interventions for the youth depression population.

Transcranial Direct Current Stimulation: Mechanisms and Psychiatric Applications.

Transcranial direct current stimulation (tDCS) involves the application of weak electric current to the scalp. tDCS may influence brain functioning through effects on cortical excitability, neural plasticity, and learning. Evidence in adults suggests promising therapeutic applications for depression, and the adverse effect profile is generally mild. Early research indicates complex interactions between tDCS and concurrent cognitive and motor tasks. Further investigation is warranted to understand how tDCS impacts processes relevant to psychiatric conditions.

Transcranial Direct Current Stimulation in Child and Adolescent Psychiatric Disorders.

Research involving transcranial direct current stimulation (tDCS) in child and adolescent psychiatry is limited. Early, short-term studies have found tDCS to be safe and well-tolerated in youth with neurodevelopmental disorders (attention-deficit hyperactivity disorder, autism, learning disorders). Preliminary data suggest potential utility in symptom reduction and improving cognitive function. Further careful research considering implications for the developing brain is necessary.

Paired-Associative Stimulation-Induced Long-term Potentiation-Like Motor Cortex Plasticity in Healthy Adolescents.

OBJECTIVE: The objective of this study was to evaluate the feasibility of using paired-associative stimulation (PAS) to study excitatory and inhibitory plasticity in adolescents while examining variables that may moderate plasticity (such as sex and environment). METHODS: We recruited 34 healthy adolescents (aged 13-19, 13 males, 21 females). To evaluate excitatory plasticity, we compared mean motor-evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS) before and after PAS at 0, 15, and 30 min. To evaluate inhibitory plasticity, we evaluated the cortical silent period (CSP) elicited by single-pulse TMS in the contracted hand before and after PAS at 0, 15, and 30 min. RESULTS: All participants completed PAS procedures. No adverse events occurred. PAS was well tolerated. PAS-induced significant increases in the ratio of post-PAS MEP to pre-PAS MEP amplitudes (p < 0.01) at all post-PAS intervals. Neither socioeconomic status nor sex was associated with post-PAS MEP changes. PAS induced significant CSP lengthening in males but not females. CONCLUSION: PAS is a feasible, safe, and well-tolerated index of adolescent motor cortical plasticity. Gender may influence PAS-induced changes in cortical inhibition. PAS is safe and well tolerated by healthy adolescents and may be a novel tool with which to study adolescent neuroplasticity.

Transcranial Direct Current Stimulation: Considerations for Research in Adolescent Depression.

Adolescent depression is a prevalent disorder with substantial morbidity and mortality. Current treatment interventions do not target relevant pathophysiology and are frequently ineffective, thereby leading to a substantial burden for individuals, families, and society. During adolescence, the prefrontal cortex undergoes extensive structural and functional changes. Recent work suggests that frontolimbic development in depressed adolescents is delayed or aberrant. The judicious application of non-invasive brain stimulation techniques to the prefrontal cortex may present a promising opportunity for durable interventions in adolescent depression. Transcranial direct current stimulation (tDCS) applies a low-intensity, continuous current that alters cortical excitability. While this modality does not elicit action potentials, it is thought to manipulate neuronal activity and neuroplasticity. Specifically, tDCS may modulate N-methyl-d-aspartate receptors and L-type voltage-gated calcium channels and effect changes through long-term potentiation or long-term depression-like mechanisms. This mini-review considers the neurobiological rationale for developing tDCS protocols in adolescent depression, reviews existing work in adult mood disorders, surveys the existing tDCS literature in adolescent populations, reviews safety studies, and discusses distinct ethical considerations in work with adolescents.

Engineered micro- and nanoscale diamonds as mobile probes for high-resolution sensing in fluid.

The nitrogen-vacancy (NV) center in diamond is an attractive platform for quantum information and sensing applications because of its room temperature operation and optical addressability. A major research effort focuses on improving the quantum coherence of this defect in engineered micro- and nanoscale diamond particles (DPs), which could prove useful for high-resolution sensing in fluidic environments. In this work we fabricate cylindrical diamonds particles with finely tuned and highly reproducible sizes (diameter and height ranging from 100 to 700 and 500 nm to 2 µm, respectively) using high-purity, single-crystal diamond membranes with shallow-doped NV centers. We show that the spin coherence time of the NV centers in these particles exceeds 700 µs, opening the possibility for the creation of ultrahigh sensitivity micro- and nanoscale sensors. Moreover, these particles can be efficiently transferred into a water suspension and delivered to the region to probe. In particular, we introduce a DP suspension inside a microfluidic circuit and control position and orientation of the particles using an optical trapping apparatus. We demonstrate a DC magnetic sensitivity of 9 µT/√Hz in fluid as well as long-term trapping stability (>30 h), which paves the way toward the use of high-sensitivity pulse techniques on contactless probes manipulated within biological settings.

The role of transcranial magnetic stimulation in treatment-resistant depression: a review.

Major depressive disorder (MDD) is a prevalent mental illness associated with significant impairment in quality of life and treatment resistance in as many as 50% of patients. Few alternatives to psychopharmacological and electroconvulsive therapy (ECT) exist. Transcranial magnetic stimulation (TMS) is one such alternative with demonstrated efficacy in the treatment of both MDD and treatment- resistant depression (TRD). Accrued evidence from meta-analyses suggests that rTMS has moderate effect sizes in both MDD and TRD, comparable, though less robust, to those seen in ECT treated patients, and similar to those seen with antidepressant treatment in TRD. To date, rTMS has been used in adult, pediatric, and geriatric populations with success. Predictors of response include lower age, lower degrees of treatment resistance, and the absence of comorbid anxiety or psychotic symptoms. rTMS is cost-effective when compared to existing treatments for TRD including psychopharmacological interventions and ECT. More research, however, is needed to determine the most optimal stimulation parameters. Accelerated treatment over a short duration of time, sequential bilateral stimulation, extended number of pulses per session are potential methods of optimizing efficacy over current unilateral stimulation protocols. The extent to which rTMS can be pushed to engender the greatest possible clinical effects while avoiding seizure induction remains unknown.

Coupling of silicon-vacancy centers to a single crystal diamond cavity.

Optical coupling of an ensemble of silicon-vacancy (SiV) centers to single-crystal diamond microdisk cavities is demonstrated. The cavities are fabricated from a single-crystal diamond membrane generated by ion implantation and electrochemical liftoff followed by homo-epitaxial overgrowth. Whispering gallery modes spectrally overlap with the zero-phonon line (ZPL) of the SiV centers and exhibit quality factors ∼ 2200. Lifetime reduction from 1.8 ns to 1.48 ns is observed from SiV centers in the cavity compared to those in the membrane outside the cavity. These results are pivotal in developing diamond integrated photonics networks.

Homoepitaxial growth of single crystal diamond membranes for quantum information processing.

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.